The present invention relates, generally, to internal combustion engines, and more particularly, to internal combustion engines used in snow blowers, generators, vegetation cutting devices such as lawn mowers, or other outdoor power equipment.
Internal combustion engines are a common power source for various types of outdoor power equipment, such as lawn mowers or lawn tractors. In the engine industry, the engine manufacturer is usually different than the original equipment manufacturer (xe2x80x9cOEMxe2x80x9d). The engine manufacturer typically supplies engines to several different OEMs, all of which have different requirements for the location and placement of the engine. Redesigning engines to fit into confined spaces of existing OEM devices, such as lawn mowers or lawn tractors, significantly increases costs for the engine manufacturer. Thus, it is desirable for an engine manufacturer to have a flexible engine design and manufacturing method which can be easily modified to make engines that accommodate a variety of existing devices.
Cylinder heads for engines are commonly made using a die casting method. When die casting, it is cost effective to maximize the number of parts fabricated with each die tool, and to use simple, compact die tools. Therefore, the layout of the die tool is an important factor in designing a part. Die casting prior art cylinder heads often requires an intake runner core or insert that must be inserted diagonally (xe2x80x9cdiagonal slidexe2x80x9d) relative to the die opening direction. A diagonal slide can create a variety of parts, but it makes the tooling more complex and requires extra space and limits the number of parts each tool can make at the same time. Using straight slides, which move transverse to the die opening direction, restricts some prior art design options, but maximizes the efficiency of each die tool.
The present invention solves some of the problems of redesigning engines to fit existing OEM devices by forming an intake runner cavity that is relatively large, and then filling at least some of the cavity space with a runner filler to form and position the intake passageway as desired. The present invention allows the same die tool to make cylinder heads with different intake positions. The cylinder heads are also die cast using straight slides to maximize the number of parts made with each simple, compact die tool.
An important factor when an OEM selects an engine to use on a specific device is the location of certain engine parts, such as the intake position, mounting brackets, and drive shaft. An engine may not be compatible with an OEM device (e.g. a lawnmower deck) because existing features of the device interfere with parts of the engine. For example, there may not be enough room near the engine""s intake position for a carburetor and fuel tank. This invention provides the flexibility to alter the intake position of an engine without redesigning the engine. This invention also enables a cylinder head incorporating the invention to be readily connected to a carburetor which would otherwise be at a different elevation than the intake passageway. Therefore, the engine can be used on a wider range of OEM devices.
The cylinder head assembly of the present invention includes a cylinder head and an adapter. The cylinder head has an entrance, an intake runner, and an intake port. The entrance is an opening on a side of the cylinder head. The intake runner, which connects the entrance to the intake port, decreases in cross-sectional area from the entrance to the intake port. The intake port is disposed between the intake runner and the combustion chamber.
The adapter is interconnected with the cylinder head and includes an inlet, a spacer, and a runner filler which is disposed within the intake runner. The inlet receives the air/fuel mixture from the carburetor. The spacer lies against the face of the cylinder head and acts as a thermal insulator for the carburetor. The runner filler is disposed within the cylinder head and at least partially forms the intake passageway that leads from the inlet to the intake port, and has a substantially uniform cross-sectional area.
In a preferred embodiment, the entrance is elliptical in cross-sectional shape. The intake runner cross-sectional area decreases between the elliptical entrance and the circular intake port. The adapter inlet is preferably a cylindrical opening that opens into the intake passageway. The runner filler is disposed within the intake runner, and at least part of the intake passageway surface is defined by the intake runner and runner filler. The crosssectional area of the intake passageway is substantially circular and substantially uniform.
In another embodiment, the entrance and intake runner can be of any shape. At the pentrance, the height dimension is larger than the width dimension. As the intake runner progresses from the entrance towards the intake port, the height dimension decreases until it is substantially the same as the width dimension.
In another embodiment, the entrance could be circular in cross-section, and the intake runner could be circular in cross-section at least near the entrance. The entrance could possibly be any shape, although an important factor is how the shape of the intake passageway affects the flow of the air/fuel mixture. The intake runner cross-sectional area could decrease in any manner, but again, an important factor is how the shape affects the air/fuel flow in the intake passageway.
In another embodiment of the present invention, at least a portion of the intake passageway is entirely enclosed within the runner filler. The runner filler completely defines at least a segment of the intake passageway between the inlet and the intake port. The intake runner may be any shape as long as the intake passageway maintains a substantially uniform cross-sectional area in the runner filler, and leading from the inlet to the intake port.
Another alternate embodiment of the present invention changes the orientation of the intake runner and adapter. In a preferred embodiment discussed above, a line containing the height dimension of the entrance is substantially transverse to a longitudinal axis of a piston cylinder. In this alternate embodiment, a line containing the height dimension of the entrance is substantially parallel to a longitudinal axis of a piston cylinder. The intake runner and adapter may also be oriented at any angle between those two locations.
In a carburetor engine, the air/fuel mixture is regulated by the carburetor, and anything that disrupts the air/fuel flow in the intake passageway of a carburetor engine may reduce engine efficiency by creating flow losses or by altering the air/fuel mixture.
The present invention provides a substantially straight and uniform passageway from the carburetor to the cylinder. This objective is achieved by altering the intake position while maintaining a relatively short and straight intake passageway.
The ability to alter the cylinder head""s intake position allows the engine manufacturer to use existing engine designs for different OEM devices. This feature of the invention reduces costs for the engine manufacturer and OEMs and increases flexibility to adapt an engine to an OEM device.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings.